Purified tetrodotoxin binding protein, a constituent part of the voltage-sensitive sodium channels of eel electroplax will be characterized with respect to its constituent polypeptide chains and the amino acid and other components of these. It will be determined whether the purified protein contains binding sites for toxin that affect gating properties of sodium channels. The binding site for tetrodotoxin will be identified by chemical methods. Antibodies specific to the purified protein and to its constituent polypeptides will be produced in experimental animals.